//----------------------------------------------------------------------------//
//                                                                            //
// ozz-animation is hosted at http://github.com/guillaumeblanc/ozz-animation  //
// and distributed under the MIT License (MIT).                               //
//                                                                            //
// Copyright (c) Guillaume Blanc                                              //
//                                                                            //
// Permission is hereby granted, free of charge, to any person obtaining a    //
// copy of this software and associated documentation files (the "Software"), //
// to deal in the Software without restriction, including without limitation  //
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// and/or sell copies of the Software, and to permit persons to whom the      //
// Software is furnished to do so, subject to the following conditions:       //
//                                                                            //
// The above copyright notice and this permission notice shall be included in //
// all copies or substantial portions of the Software.                        //
//                                                                            //
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR //
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,   //
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// DEALINGS IN THE SOFTWARE.                                                  //
//                                                                            //
//----------------------------------------------------------------------------//

#ifndef OZZ_OZZ_ANIMATION_RUNTIME_SKELETON_H_
#define OZZ_OZZ_ANIMATION_RUNTIME_SKELETON_H_

#include "SkrAnim/ozz/export.h"
#include "SkrAnim/ozz/base/io/archive_traits.h"
#include "SkrAnim/ozz/base/platform.h"
#include "SkrAnim/ozz/base/span.h"

namespace ozz
{
namespace io
{
class IArchive;
class OArchive;
} // namespace io
namespace math
{
struct SoaTransform;
}
namespace animation
{

// Forward declaration of SkeletonBuilder, used to instantiate a skeleton.
namespace offline
{
class SkeletonBuilder;
}

// This runtime skeleton data structure provides a const-only access to joint
// hierarchy, joint names and rest-pose. This structure is filled by the
// SkeletonBuilder and can be serialize/deserialized.
// Joint names, rest-poses and hierarchy information are all stored in separate
// arrays of data (as opposed to joint structures for the RawSkeleton), in order
// to closely match with the way runtime algorithms use them. Joint hierarchy is
// packed as an array of parent jont indices (16 bits), stored in depth-first
// order. This is enough to traverse the whole joint hierarchy. See
// IterateJointsDF() from skeleton_utils.h that implements a depth-first
// traversal utility.
class OZZ_ANIMATION_DLL Skeleton
{
public:
    // Defines Skeleton constant values.
    enum Constants
    {

        // Defines the maximum number of joints.
        // This is limited in order to control the number of bits required to store
        // a joint index. Limiting the number of joints also helps handling worst
        // size cases, like when it is required to allocate an array of joints on
        // the stack.
        kMaxJoints = 1024,

        // Defines the maximum number of SoA elements required to store the maximum
        // number of joints.
        kMaxSoAJoints = (kMaxJoints + 3) / 4,

        // Defines the index of the parent of the root joint (which has no parent in
        // fact).
        kNoParent = -1,
    };

    // Builds a default skeleton.
    Skeleton() = default;

    // Allow move.
    Skeleton(Skeleton&&);
    Skeleton& operator=(Skeleton&&);

    // Disables copy and assignation.
    Skeleton(Skeleton const&)            = delete;
    Skeleton& operator=(Skeleton const&) = delete;

    // Declares the public non-virtual destructor.
    ~Skeleton();

    // Returns the number of joints of *this skeleton.
    int num_joints() const { return static_cast<int>(joint_parents_.size()); }

    // Returns the number of soa elements matching the number of joints of *this
    // skeleton. This value is useful to allocate SoA runtime data structures.
    int num_soa_joints() const { return (num_joints() + 3) / 4; }

    // Returns joint's rest poses. Rest poses are stored in soa format.
    span<const math::SoaTransform> joint_rest_poses() const
    {
        return joint_rest_poses_;
    }

    // Returns joint's parent indices range.
    span<const int16_t> joint_parents() const { return joint_parents_; }

    // Returns joint's name collection.
    span<const char* const> joint_names() const
    {
        return span<const char* const>(joint_names_.begin(), joint_names_.end());
    }

    // Serialization functions.
    // Should not be called directly but through io::Archive << and >> operators.
    void Save(ozz::io::OArchive& _archive) const;
    void Load(ozz::io::IArchive& _archive, uint32_t _version);

private:
    // Internal allocation/deallocation function.
    // Allocate returns the beginning of the contiguous buffer of names.
    char* Allocate(size_t _char_count, size_t _num_joints);
    void  Deallocate();

    // SkeletonBuilder class is allowed to instantiate an Skeleton.
    friend class offline::SkeletonBuilder;

    // Allocation for the whole skeleton.
    void* allocation_ = nullptr;

    // Buffers below store joint informations in joing depth first order. Their
    // size is equal to the number of joints of the skeleton.

    // Rest pose of every joint in local space.
    span<math::SoaTransform> joint_rest_poses_;

    // Array of joint parent indexes.
    span<int16_t> joint_parents_;

    // Stores the name of every joint in an array of c-strings.
    span<char*> joint_names_;
};
} // namespace animation

namespace io
{
OZZ_IO_TYPE_VERSION(2, animation::Skeleton)
OZZ_IO_TYPE_TAG("ozz-skeleton", animation::Skeleton)
} // namespace io
} // namespace ozz
#endif // OZZ_OZZ_ANIMATION_RUNTIME_SKELETON_H_
